The present invention relates to growing vines trained in rows, and more particularly to a growing method intended specifically to avoid frost damage and to promote good fruiting.
A known growing method consists in covering the rows of vines in waterproof film of plastics material draped over support wires extending between stakes, the film forming a tunnel that operates by the greenhouse effect to keep the temperature of the vines above the temperature at which buds are destroyed by frost. That method of growing does not provide complete satisfaction.
It has been observed that the greenhouse effect is liable to subject the vines, on sunny days, to excessive temperatures capable of having an unfavorable influence on the quality of the wine produced, and in particular having the effect of reducing the richness of its aromas.
The invention seeks to avoid various difficulties that are encountered in growing vines, but without thereby spoiling the quality of the resulting wine.
The invention achieves this by a method of growing vines trained in rows, the method serving in particular to avoid frost damage and to promote good fruiting, the method being of the type consisting in draping a film of plastics material over each row of vines, the film being supported firstly by at least one top wire situated at the top of a row of stakes, and secondly by spreader elements for spreading the two panels of the film, the film being held by fasteners secured at intervals to the bottom edges of the film and connected to fastener members preferably situated on said stakes, the method being characterized by the fact that said bottom edges of the film are disposed substantially level with and preferably slightly below the lowest height at which side shoots develop, while leaving between said edges a large opening allowing air to flow because the side portions of the film situated above the spreader elements are provided with orifices enabling the vines inside the film to be ventilated, which film is put into place shortly before new growth starts and is left in place at least until the end of any risk of frost.
By means of the invention, in spite of the vines being ventilated via said orifices, the consequences of spring frosts are avoided or greatly limited, which frosts would otherwise usually run the risk of occurring at the moment when new growth starts.
According to the invention, the film is preferably left in place until after the fruiting period so as to enable fruiting to take place under favorable circumstances.
Preferably, a film is used whose top portion possesses orifices having a total area that corresponds to a value lying in the range 100 cm2 to 1000 cm2 per linear meter of film, and that preferably lies in the range 200 cm2 to 500 cm2 per linear meter of film.
Preferably, the orifices are situated in each of the panels of the film.
To facilitate ripening of the grapes, after the vines have been grown to the beginning of ripening, the above-mentioned film is preferably placed on the top wire of the row of vines, the wire being raised so as to be situated above the leaves of the vines, the film resting laterally on said spreader elements, and being held via its bottom edges by said fasteners, the bottom edges of the film being at a level situated above the grapes, and the film is removed immediately before vintaging.
In a particular implementation of the method of the invention, a plastics film is extended on the ground between the rows of vines to remove water to the ends of the rows to avoid the water penetrating into the ground.
Surprisingly, it has been observed that vines provided with a film of the invention are much less sensitive to frost and, for example, can withstand temperatures of xe2x88x923xc2x0 C., even though the temperature of the air in the vicinity of the vegetation under the film is only 1xc2x0 C. higher than the outside ambient temperature.
Most surprisingly, the invention also makes it possible to improve fruiting by avoiding the phenomena known as xe2x80x9cabortionxe2x80x9d and xe2x80x9cuneven ripeningxe2x80x9d which correspond to the fact of a greater or lesser fraction of the vine flowers failing to set seed, or to the fact that the flowers set seed in a manner that is highly staggered over time which leads at vintaging time to bunches containing some grapes that are over-ripe while other grapes are still not yet ripe.
Tests performed by the Applicant have shown that implementing the method of the invention ensures fruiting of vines that is particularly regular and complete, even under climatic conditions that are not very favorable.
Implementing the method of the invention also has the advantage of considerably reducing requirements concerning the amount of treatment against the various diseases of the vine that turns out to be necessary. In particular, it has been found that a single fungicidal treatment prior to installation of the film suffices, and no further treatment is needed until the film is removed, e.g. at the end of May or the beginning of June which, independently of any ecological advantages, constitutes a very considerable saving in pesticide and labor costs.
The method of the invention also has the advantage of ensuring that vines grow more regularly and of causing the growth cycle thereof to be advanced by at least eight to ten days, thereby making it possible to pick earlier and thus generally under weather conditions that are better, which can be particularly advantageous for late varieties of grape.
Using the same films and the same support devices, the method of the invention makes it possible to avoid subjecting grapes that are maturing to sometimes heavy rain that can lead to the drawbacks both of reducing alcohol content and of encouraging rotting by excess moisture and some of the grapes bursting.
The invention also provides apparatus for implementing the above-specified method.
In a particular embodiment, the apparatus comprises strips of film for draping over the rows of vines, the strips being provided along their length and in the middle region thereof with orifices, spreader elements for holding the two panels of film apart, fasteners for holding the film via its bottom edges, and adjustable height support means for supporting the top wire that extends between the stakes in a row of vines.
In a particular embodiment, the apparatus further includes strips of film for placing on the ground between the rows of vines to remove rain water to the ends of the